This invention is directed to a synthetic multifilament yarn containing a novel finishing composition, and more specifically to a spin finish for multifilament yarn used in food packaging. Still more specifically, this invention is directed to a finishing composition comprising butyl stearate, sorbitan monooleate and polyoxyethylene (18-22) sorbitan monooleate, for multifilamentary yarns made from synthetic linear polymers including, for example, polyamides, polyesters, polyolefins, and other polymers useful in food packaging.
In the manufacture of yarn filaments including, for example, filaments made from linear polymers such as the polyesters and polyamides, the ultimate strength of the yarn can be substantially improved by subjecting the filaments to drawing techniques to increase their molecular orientation. Although the drawing operation may be conducted by various means, the common procedure comprises devices commonly known as feed and draw rolls for advancing the filaments. The filaments are stretched by running the rolls at differential speeds with the degree of drawing depending upon the ratio of the peripheral speeds of said rolls. In order to localize the point at which the stretching or drawing occurs, a draw point localizer is normally used. For example, a device may be placed between the feed and draw roll which is known as a draw pin around which the yarn is wrapped. This pin introduces a frictional drive on the moving filaments which causes drawing to take place in areas of the pin. It is well known that the drawing operation can be facilitated when the temperature of the yarn is elevated. The application of heat may be accomplished by various means, e.g., a hot plate placed between the feed and draw rolls.
One of the problems encountered during drawing, either at ambient or elevated temperatures is the frequent occurrence of filament breakage. Thus, during drawing, one or more of the individual filaments of the thread line may break and wrap around the draw rolls or the entire thread line may break which requires stoppage until adjustments can be made. One of the causes of filament breakage during the drawing process is the buildup of an extensive amount of tension on the yarn, which is due for the most part to the interfilamentary friction and yarn-to-metal friction. Excessive tensions resulting from the development of high frictions during the drawing can be reduced, however, by applying to the yarn various antifriction compositions. These compositions are generally applied via an aqueous medium prior to drawing. Although there are presently available various finishing compositions which may be used to reduce yarn tension buildup during drawing, there is a need for compositions capable of not only lowering the yarn to metal friction, but also consisting of ingredients suitable for use on yarn to be used in food packaging, where all ingredients must be approved by the Food and Drug Administration (FDA) for use as direct or indirect food additives.